OOOPS, I forgot to leave a message over on the Coriolis Thread that it had been continued in this thread. These responses are too interesting to let the software gobble up, so I am pasting them here.Subject Re: Sinusoidal tides
Posted by dxb (journeyman)
Posted on Mon Apr 29 11:25:56 2002
Dear faldage,
High Tides along the south coast of the UK:
This is all strictly non-technical and whether it will assist you in universal understanding I hesitate to predict! I don't think it helped me much - knowledge is one thing, understanding another.
What I am told and what I read do not seem to agree. An amateur yachtsman has assured me, I think mistakenly, that the high tide along the south coast moves from west to east. The Atlantic high tide he tells me swells back around both sides of Ireland and around the north of Scotland, moving up the channel and down the North Sea (would this form a sort of mælstrom where they meet, I wonder?). When I look at tide tables for south coast ports, however, my interpretation is that the tide moves east to west along the Channel coast. I think I prefer to trust the tide tables and to avoid cruising on my friend’s yacht!
It seems from the tables that there is a high tide approximately every 12 hours 20 minutes. The double tide effect at Poole Harbour causes a secondary peak that occurs about 4 hours after the main high tide. I don't know why it occurs, perhaps Bean can explain; it is generally lower than the main peak, but there appears to be variation in this, I guess depending on where you are in the spring/neap tide cycle. A similar effect is seen at Southampton due I believe to the Isle of Wight and the two arms of the Solent, but there the two peaks are mostly about the same height with a drop of only a few inches between them, so this has the effect of lengthening the duration of high water – obviously very desirable for a port. Again this effect seems more or less marked depending, I guess, on the spring/neap cycle.
Where I have given conclusions rather than facts above they are based on my deductions arrived at from looking at the tide tables so could well be completely erroneous!
Two interesting links:
http://www.ukho.gov.uk/easytide.html
http://www.alia.ie/sailing/tides.html
dxb
Subject Re: Sinusoidal tides
Posted by Bean (addict)
Posted on Mon Apr 29 12:32:31 2002
This has been very interesting indeed! From a glance at the dimensions of Poole Harbour, I would at first guess that the situation is much, much more complicated than first appears.
I Googled "double tides" and got this great link for a place in Scotland, which at least states that it's due to the what we call the bottom topography (which is what I suspected all along): http://www.rampantscotland.com/know/blknow31.htm
I think to get a good, definitive answer to your question may take some hunting in research papers. Perhaps someone's done a model of the water level and currents in Poole Harbour for a thesis or something. Indeed, from the bit I've read in my book (an introductory oceanography book with merely a single chapter on tides) it would be quite complicated! And from looking at the map, with two sets of narrows and Brownsea island in the middle - I'd say it must be quite complicated - no simple rectangular box for this model!
Edit: Oh! Oh! I've found something great, and not technical! Try http://www.weston.org.uk/tides.htm. (I am reading it right now, haven't finished it yet. Just wanted to post in case you were still on Board!)
Subject Re: Sinusoidal tides
Posted by Bean (addict)
Posted on Mon Apr 29 13:08:03 2002
OK, dxb, here you go. Online, I found a reference to a book:
Author = Officer, Charles B.
Title = Physical Oceanography of Estuaries (and Associated Coastal Waters)
Publisher = John Wiley & Sons
Year = 1976
Pages = 465
ISBN = 0-471-65278-4
Apparently, it has a chapter which has a section dealing with tides at Solent, etc. So there you go! In a free moment maybe you or I will pick it up from a university library and have a gander at it!
For those of you that are new to the board, the software allows for more than 99 responses to a post, but just try and retrieve them at a later date! You will find yourself in some other thread, in some other time and the responses will be crying in the woods, wishing they hadn't used breadcrumbs to mark their way!
OP
